the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 11 Aug 2025
Water flow timing, quantity, and sources in a fractured high mountain permafrost rock wall
Abstract. Water flow in high mountain rock walls is crucial in landscape evolution and slope stability. However, the timing, quantity, and sources of this flow remain poorly understood. In the Mont Blanc massif, tunnels at the Aiguille du Midi peak (3842 m) provide direct access to steep permafrost-affected rock walls. Over two years (May 2022–October 2023), we monitored water flowing from fractures using a real-time system measuring flow rate, temperature, electrical conductivity, and fluorescent tracers, together with meteorological data and ground surface temperatures. Results indicate high surface–subsurface connectivity. The water source is primarily snowmelt, with additional inputs from late-summer rainfall. Electrical conductivity, stable isotopes, and recession curve analysis suggest another source of older subsurface ice. Flow onset was closely tied to ATs, with steady diurnal fluctuations appearing once ground surface temperatures exceeded 0 °C. Lag times between daily peaks of flow rate and peaks of air and ground surface temperatures of 3–9 hours and 0–3 hours, respectively, point to rapid unsaturated infiltration conditions. Distinct flow regimes observed in two adjacent fracture systems reflect a complex, heterogeneous network, including sediment-filled fractures with delayed response. Significant flow rate (often >10 L/h) and water temperature often exceeding 5 °C, suggest a significant heat transfer by advection, capable of enhancing permafrost degradation. This study provides rare direct observations of fracture flow dynamics in steep permafrost rocks, improving understanding of water routing and its response to atmospheric forcing. The findings offer valuable constraints for coupled hydrothermal models, permafrost-related hazard assessments, and the potential impact of climate change.
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Notice on discussion status
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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Preprint
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Supplement
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
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- Final revised paper
Journal article(s) based on this preprint
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2025-2450', Marcia Phillips, 12 Aug 2025
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AC1: 'Reply on RC1', Matan Ben-Asher, 25 Sep 2025
Dear Marcia Phillips,
We sincerely thank you for your thorough and constructive review. Your detailed comments have been very helpful in improving the clarity, structure, and scientific depth of our manuscript.
We have carefully addressed each point in a separate response document (attached). In this document, we provide a point-by-point reply and, for clarity, include all revised figures with their updated captions at the end.
We are grateful for your valuable input, which has substantially strengthened the paper.
Best regards,
Matan Ben-Asher (on behalf of all co-authors)-
RC3: 'Reply on AC1', Marcia Phillips, 26 Sep 2025
Dear Authors,
thanks for making these changes. I noticed the following typos/small errors in your figures/figure captions:
Figure 3: both terraces are labelled as 'upper terrace' (no lower terrace). Figure 4 caption: ... equipped with temperature and... Figure 5B and 5C: why not use a bold blue line for both to represent Air T? Figure 5, caption: ...during the snow melt season in 2022 (same for 2023) / ... which marks the melting of the snowpack (not thawing). Figure 6A: please fix the layout of the legend. Figure 8: the whole figure is fuzzy (screen shot?), please label the x-axis correctly. ... the vertical axis represents the lag time in hours... Why is Air temperature written in green? (gives the impression of there being a link with the green frame).
Re the roof in the tunnel: I felt it would be useful to mention its raison d'être briefly, because you use the roof to collect your water infiltration data and because the roof is there to prevent water infiltration from reaching the tourists.
Kind regards, Marcia Phillips
Citation: https://doi.org/10.5194/egusphere-2025-2450-RC3 -
AC3: 'Reply on RC3', Matan Ben-Asher, 27 Sep 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-2450/egusphere-2025-2450-AC3-supplement.pdf
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AC4: 'Reply on AC3', Matan Ben-Asher, 27 Sep 2025
Dear Marcia,
Thank you very much for your quick response and for pointing out these minor issues in the revised figures. We have carefully checked and corrected them as follows:
Figure 3: corrected the labels of the terraces (upper and lower).
Figure 4 caption: revised to read “…equipped with temperature and …”, and a sentence was added explaining that the metal roof was installed to prevent water infiltration from reaching tourists, and that we used this structure for our measurements.
Figure 5B and 5C: changed to bold blue lines for air temperature in both panels; caption updated to “…during the snowmelt season in 2022 (and similarly for 2023)” and “…which marks the melting of the snowpack.”
Figure 6A: adjusted the layout of the legend for clarity.
Figure 8: re-exported at high resolution (not a screenshot), corrected the x-axis label, changed the labels of the vertical axis to "lag time (hours), and changed the air temperature series to a neutral color (black) to avoid confusion with the green frame.
Please find attached the file with all corrected figures in my previous reply.
Thank you again for your quick and attentive comments, which helped us further improve the quality and clarity of the manuscript.
Best regards,
Matan Ben-Asher (on behalf of all co-authors)Citation: https://doi.org/10.5194/egusphere-2025-2450-AC4
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AC4: 'Reply on AC3', Matan Ben-Asher, 27 Sep 2025
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AC3: 'Reply on RC3', Matan Ben-Asher, 27 Sep 2025
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RC3: 'Reply on AC1', Marcia Phillips, 26 Sep 2025
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AC1: 'Reply on RC1', Matan Ben-Asher, 25 Sep 2025
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RC2: 'Comment on egusphere-2025-2450', Anonymous Referee #2, 11 Sep 2025
The paper by Ben-Asher et al. investigates the flow dynamics and surface-subsurface connectivity in a fractured domain located in a steep permafrost-affected high-altitude system in the Aguille du Midi site (Mont Blanc Massif). The Authors present a rare and intersting dataset resulting from a two-year set of temporally resolved measurements of flow rate, temperature, electrical conductivity, tracer fluorescence, and isotope analyses. These data, along with meteorological data, are then analyzed to infer the amount of surface water infiltrating through permafrost-affected rock walls.
I think the work would benefit from a set of revisions which range between major, moderate and minor, as detailed in the attachment.
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AC2: 'Reply on RC2', Matan Ben-Asher, 25 Sep 2025
Dear Reviewer,
Thank you very much for your constructive feedback on our manuscript. Your comments helped us to improve both the clarity of the methods and the presentation of the results.
We have addressed all points in detail in the attached response document. This file contains our point-by-point replies and, for clarity, includes all revised figures with their updated captions at the end.
We are grateful for your helpful review, which has significantly improved the manuscript.
Best regards,
Matan Ben-Asher (on behalf of all co-authors)
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AC2: 'Reply on RC2', Matan Ben-Asher, 25 Sep 2025
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RC4: 'Comment on egusphere-2025-2450', Riccardo Scandroglio, 28 Sep 2025
The manuscript by Ben-Asher et al. presents a detailed investigation of water flow dynamics within a fractured permafrost rock wall at the Aiguille du Midi, Mont Blanc Massif. Using a multi-method approach, the authors examine the sources and timing of water flow in a high alpine permafrost environment. The methodology is innovative within the context of permafrost research, and the dataset is both rare and valuable. The study makes a meaningful contribution to our understanding of water infiltration processes in permafrost-affected bedrock.
However, several aspects of the manuscript require significant improvement before it can be considered for publication.
First, many of the results are not adequately supported by graphical representation or statistical analysis. Key claims are made without sufficient visual or quantitative evidence, leaving the reader unable to verify the conclusions (e.g., Tables 2, S1, S2, S3). Additionally, several numerical values lack precision and are often presented without measures of variability (such as standard deviation or coefficient of variation), despite the fact that the processes under study are known to exhibit high variability.
Second, the graphical presentation of results is limited and in need of substantial improvement. Overall, the figures do not sufficiently support the analysis and should be revised for clarity and readability. For example, Figure 5 and 7 both show water flow and air temperature, but in neither case are the values clearly legible or effectively presented.
The text also requires revision. The introduction is overly general and lacks site-specific details—such as fracture characteristics or distances between loggers and snow cover—that are critical to contextualizing the study. Sections 4.1.3 and 4.1.4 are particularly difficult to follow and include figures that do not appear directly relevant. Furthermore, the separation between results and discussion is not always maintained; some interpretive content appears in the results section, while parts of the discussion are descriptive rather than analytical. The discussion would also benefit from comparisons with similar studies to better situate the findings within the existing literature.
Although the manuscript is mostly well-written, it would benefit from a thorough proofreading to address grammatical, stylistic, and consistency issues.
In summary, this paper presents a unique and promising dataset with strong potential to advance the field, but requires major revisions in terms of structure, data presentation, and clarity, as listed in the attached file. I recommend the manuscript be accepted pending major revisions.
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AC5: 'Reply on RC4', Matan Ben-Asher, 02 Dec 2025
Dear Riccardo Scandroglio,
We sincerely thank you for your thoughtful and detailed review. Your comments were highly constructive and have been very helpful in improving the clarity, analysis, and overall quality of our manuscript.
We have carefully addressed each of your points in a separate response document (attached). For clarity, this document includes our point-by-point replies as well as all revised figures with their updated captions.
We greatly appreciate the time and expertise you invested in this review, and your input has substantially strengthened the manuscript.
Best regards,
Matan Ben-Asher (on behalf of all co-authors) - AC6: 'Reply on RC4', Matan Ben-Asher, 02 Dec 2025
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AC5: 'Reply on RC4', Matan Ben-Asher, 02 Dec 2025
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2025-2450', Marcia Phillips, 12 Aug 2025
The paper entitled 'Water flow timing, quantity, and sources in a fractured high mountain permafrost rock wall' by Ben-Asher et al. presents the results of a two-year campaign monitoring fracture water in high elevation permafrost at the Aiguille du Midi, France. The subject is currently of great interest, as rock slope failures in high mountain areas appear to be linked to the loss of sealing permafrost ice plugs in rock fractures and to deep-seated infiltration of water into the newly accessible fracture systems. The extent of the fracture systems and their hydrology is poorly known. This study uses a combination of methods to identify the sources of water flowing through rock fractures, the rates and timing of flow, preferential flowpaths, and the thermal regimes of the rock and water. Most of the relevant literature is cited (see my suggestions in the detailed comments (attached) for further literature), but in some cases the references do not appear (error message). Most of the figures need enlarging and labelling to improve their legibility. The figure captions do not adequately describe the figures. The language is mostly clear but with some grammatical or consistency issues (see detailed comments). Some small changes to the paper structure should be considered, particularly in sections 4.3.1 and 4.4, where the explanations/hypotheses should be moved to the Discussion. The paper is highly relevant and I suggest it be accepted for publication, with major modifications.
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AC1: 'Reply on RC1', Matan Ben-Asher, 25 Sep 2025
Dear Marcia Phillips,
We sincerely thank you for your thorough and constructive review. Your detailed comments have been very helpful in improving the clarity, structure, and scientific depth of our manuscript.
We have carefully addressed each point in a separate response document (attached). In this document, we provide a point-by-point reply and, for clarity, include all revised figures with their updated captions at the end.
We are grateful for your valuable input, which has substantially strengthened the paper.
Best regards,
Matan Ben-Asher (on behalf of all co-authors)-
RC3: 'Reply on AC1', Marcia Phillips, 26 Sep 2025
Dear Authors,
thanks for making these changes. I noticed the following typos/small errors in your figures/figure captions:
Figure 3: both terraces are labelled as 'upper terrace' (no lower terrace). Figure 4 caption: ... equipped with temperature and... Figure 5B and 5C: why not use a bold blue line for both to represent Air T? Figure 5, caption: ...during the snow melt season in 2022 (same for 2023) / ... which marks the melting of the snowpack (not thawing). Figure 6A: please fix the layout of the legend. Figure 8: the whole figure is fuzzy (screen shot?), please label the x-axis correctly. ... the vertical axis represents the lag time in hours... Why is Air temperature written in green? (gives the impression of there being a link with the green frame).
Re the roof in the tunnel: I felt it would be useful to mention its raison d'être briefly, because you use the roof to collect your water infiltration data and because the roof is there to prevent water infiltration from reaching the tourists.
Kind regards, Marcia Phillips
Citation: https://doi.org/10.5194/egusphere-2025-2450-RC3 -
AC3: 'Reply on RC3', Matan Ben-Asher, 27 Sep 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-2450/egusphere-2025-2450-AC3-supplement.pdf
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AC4: 'Reply on AC3', Matan Ben-Asher, 27 Sep 2025
Dear Marcia,
Thank you very much for your quick response and for pointing out these minor issues in the revised figures. We have carefully checked and corrected them as follows:
Figure 3: corrected the labels of the terraces (upper and lower).
Figure 4 caption: revised to read “…equipped with temperature and …”, and a sentence was added explaining that the metal roof was installed to prevent water infiltration from reaching tourists, and that we used this structure for our measurements.
Figure 5B and 5C: changed to bold blue lines for air temperature in both panels; caption updated to “…during the snowmelt season in 2022 (and similarly for 2023)” and “…which marks the melting of the snowpack.”
Figure 6A: adjusted the layout of the legend for clarity.
Figure 8: re-exported at high resolution (not a screenshot), corrected the x-axis label, changed the labels of the vertical axis to "lag time (hours), and changed the air temperature series to a neutral color (black) to avoid confusion with the green frame.
Please find attached the file with all corrected figures in my previous reply.
Thank you again for your quick and attentive comments, which helped us further improve the quality and clarity of the manuscript.
Best regards,
Matan Ben-Asher (on behalf of all co-authors)Citation: https://doi.org/10.5194/egusphere-2025-2450-AC4
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AC4: 'Reply on AC3', Matan Ben-Asher, 27 Sep 2025
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AC3: 'Reply on RC3', Matan Ben-Asher, 27 Sep 2025
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RC3: 'Reply on AC1', Marcia Phillips, 26 Sep 2025
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AC1: 'Reply on RC1', Matan Ben-Asher, 25 Sep 2025
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RC2: 'Comment on egusphere-2025-2450', Anonymous Referee #2, 11 Sep 2025
The paper by Ben-Asher et al. investigates the flow dynamics and surface-subsurface connectivity in a fractured domain located in a steep permafrost-affected high-altitude system in the Aguille du Midi site (Mont Blanc Massif). The Authors present a rare and intersting dataset resulting from a two-year set of temporally resolved measurements of flow rate, temperature, electrical conductivity, tracer fluorescence, and isotope analyses. These data, along with meteorological data, are then analyzed to infer the amount of surface water infiltrating through permafrost-affected rock walls.
I think the work would benefit from a set of revisions which range between major, moderate and minor, as detailed in the attachment.
-
AC2: 'Reply on RC2', Matan Ben-Asher, 25 Sep 2025
Dear Reviewer,
Thank you very much for your constructive feedback on our manuscript. Your comments helped us to improve both the clarity of the methods and the presentation of the results.
We have addressed all points in detail in the attached response document. This file contains our point-by-point replies and, for clarity, includes all revised figures with their updated captions at the end.
We are grateful for your helpful review, which has significantly improved the manuscript.
Best regards,
Matan Ben-Asher (on behalf of all co-authors)
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AC2: 'Reply on RC2', Matan Ben-Asher, 25 Sep 2025
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RC4: 'Comment on egusphere-2025-2450', Riccardo Scandroglio, 28 Sep 2025
The manuscript by Ben-Asher et al. presents a detailed investigation of water flow dynamics within a fractured permafrost rock wall at the Aiguille du Midi, Mont Blanc Massif. Using a multi-method approach, the authors examine the sources and timing of water flow in a high alpine permafrost environment. The methodology is innovative within the context of permafrost research, and the dataset is both rare and valuable. The study makes a meaningful contribution to our understanding of water infiltration processes in permafrost-affected bedrock.
However, several aspects of the manuscript require significant improvement before it can be considered for publication.
First, many of the results are not adequately supported by graphical representation or statistical analysis. Key claims are made without sufficient visual or quantitative evidence, leaving the reader unable to verify the conclusions (e.g., Tables 2, S1, S2, S3). Additionally, several numerical values lack precision and are often presented without measures of variability (such as standard deviation or coefficient of variation), despite the fact that the processes under study are known to exhibit high variability.
Second, the graphical presentation of results is limited and in need of substantial improvement. Overall, the figures do not sufficiently support the analysis and should be revised for clarity and readability. For example, Figure 5 and 7 both show water flow and air temperature, but in neither case are the values clearly legible or effectively presented.
The text also requires revision. The introduction is overly general and lacks site-specific details—such as fracture characteristics or distances between loggers and snow cover—that are critical to contextualizing the study. Sections 4.1.3 and 4.1.4 are particularly difficult to follow and include figures that do not appear directly relevant. Furthermore, the separation between results and discussion is not always maintained; some interpretive content appears in the results section, while parts of the discussion are descriptive rather than analytical. The discussion would also benefit from comparisons with similar studies to better situate the findings within the existing literature.
Although the manuscript is mostly well-written, it would benefit from a thorough proofreading to address grammatical, stylistic, and consistency issues.
In summary, this paper presents a unique and promising dataset with strong potential to advance the field, but requires major revisions in terms of structure, data presentation, and clarity, as listed in the attached file. I recommend the manuscript be accepted pending major revisions.
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AC5: 'Reply on RC4', Matan Ben-Asher, 02 Dec 2025
Dear Riccardo Scandroglio,
We sincerely thank you for your thoughtful and detailed review. Your comments were highly constructive and have been very helpful in improving the clarity, analysis, and overall quality of our manuscript.
We have carefully addressed each of your points in a separate response document (attached). For clarity, this document includes our point-by-point replies as well as all revised figures with their updated captions.
We greatly appreciate the time and expertise you invested in this review, and your input has substantially strengthened the manuscript.
Best regards,
Matan Ben-Asher (on behalf of all co-authors) - AC6: 'Reply on RC4', Matan Ben-Asher, 02 Dec 2025
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AC5: 'Reply on RC4', Matan Ben-Asher, 02 Dec 2025
Peer review completion
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Antoine Chabas
Jean-Yves Josnin
Josué Bock
Emmanuel Malet
Amaël Poulain
Yves Perrette
Florence Magnin
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(2990 KB) - Metadata XML
-
Supplement
(552 KB) - BibTeX
- EndNote
- Final revised paper
The paper entitled 'Water flow timing, quantity, and sources in a fractured high mountain permafrost rock wall' by Ben-Asher et al. presents the results of a two-year campaign monitoring fracture water in high elevation permafrost at the Aiguille du Midi, France. The subject is currently of great interest, as rock slope failures in high mountain areas appear to be linked to the loss of sealing permafrost ice plugs in rock fractures and to deep-seated infiltration of water into the newly accessible fracture systems. The extent of the fracture systems and their hydrology is poorly known. This study uses a combination of methods to identify the sources of water flowing through rock fractures, the rates and timing of flow, preferential flowpaths, and the thermal regimes of the rock and water. Most of the relevant literature is cited (see my suggestions in the detailed comments (attached) for further literature), but in some cases the references do not appear (error message). Most of the figures need enlarging and labelling to improve their legibility. The figure captions do not adequately describe the figures. The language is mostly clear but with some grammatical or consistency issues (see detailed comments). Some small changes to the paper structure should be considered, particularly in sections 4.3.1 and 4.4, where the explanations/hypotheses should be moved to the Discussion. The paper is highly relevant and I suggest it be accepted for publication, with major modifications.